The company didn’t specify where the cuts will be made, but CEO Scott Thompson said his plan is to refocus on “a select group of core businesses, the platforms that support those core businesses and the data that drives deep personalization for users” and improving return on investment for advertisers.

He said the action is “an important next step toward a bold, new Yahoo! — smaller, nimbler, more profitable and better equipped to innovate as fast as our customers and our industry require.”

This is the sixth mass layoff at the company in four years. Those being cut are to be notified today, but ZDNet reports that many are to remain with the company until their projects are completed. It would seem those folks could merely bolt for the door.

But the fate of two key parts of the soon-to-be-blown-apart unit — Yahoo’s advertising technology businesses, Right Media and APT, and its search business — is still being contemplated. Possible scenarios include a sale or a joint venture transaction for both, which employ thousands of Yahoo staffers.

Swisher says more layoffs could occur later. Next week Thompson, along with consultants from the Boston Consulting Group, will announce a reorganization of the company.